Systems in which telephones are placed in communication with computers or data terminals typically employ a component known as a data set. Data sets perform such transmitting functions as converting voice or analogue signals transmitted to and from a telephone into digital signals which are transmitted to and from a computer or data terminal. The data set also performs such supervisory functions as generating a busy signal when the computer or terminal is unavailable, and answering the telephone when the computer or terminal is available. The more sophisticated data sets also have memory means for storing and forwarding data.
Once a communication has been completed by a computer or data terminal connected with a data set and telephone, the data set must be made to recognize such completion in order to drop the telephone line and thereby free the data set for service with other telephones. For this reason the data sets are normally provided with an interconnect terminal known as a data terminal ready or DTR lead by which an oscillatory signal may be received from a computer or data terminal resetting the data set upon completion of a communication. Many data terminals, however, and indeed even some computers, do not possess a DTR reset capability. Systems using these data terminals must therefore be provided with other means for indicating the completion of a communicative transaction if they are to be used at all. This means has been in the form of a supervisory lamp mounted on the data set which is energizable by the telephone or computer status. Its illumination signals an attendant that the data set needs to be reset or is out of service.
It would, of course, be desirable to automate such data sets to eliminate the need for an operator. Though the data sets themselves could be redesigned to provide this capability, this redesign would be difficult and costly to perform on existing units. Furthermore, the provision of such an additional function through redesign would be unnecessary where the data set is used with a computer or terminal that does possess a reset function. It would therefore be desirable to device an auxillary unit or apparatus which could be coupled with the data set without having to modify existing units themselves. It is to this task to which the present invention is primarily directed.